Yahoo's new CEO Marissa Mayer's net worth is believed to be $300 million, according to therichest.org in its estimations earlier this year.

Mayer is married to tech investor Zach Bogue and serves on the board of Wal-Mart Stores, as well as on the boards of the San Francisco Museum of Modern Art and the New York City Ballet. She certainly is not taking her new role with Yahoo because she needs the money.

Many believe Yahoo's decision to appoint Google's Vice President Marissa Mayer as its new CEO is a risk. Critics wonder whether a high profile female executive would be able to succeed where a number of other leading candidates have failed. Many had believed interim chief Ross Levinsohn would be appointed for the long term position when other leading candidates pulled out. However, the young and successful Mayer has become the fifth person to take over the lead role at Yahoo in the past year alone.

The 37-year-old has posted a message on her Google+ account saying she is "incredibly excited to start my new role."

She finished off her last day at Google on Monday, and takes the hot seat immediately from today (Tuesday).

Yahoo has struggled in recent years in an increasingly competitive market, with Google stealing much of the online ad money on offer, and other young hip and cooler companies coming out, such as Facebook.

"It's a very special thing to be able to get somebody like Marissa," said Netscape founder and venture capitalist Marc Andreessen. "She'll be the first CEO they've had with a background in modern Web technology."

"Marissa is a well-known, visionary leader in user experience and product design," Yahoo co-founder David Filo said in a news release.

Interestingly Yahoo have appointed Mayer knowing she will be going on maternity leave very soon after taking over, and will give birth sometime in the coming months. In an interview with Fortune, she explained that her first child, a boy, has a due date of Oct. 7, 2012.

Mayer has said that she told this directly to the Yahoo board in June and that it had already been agreed that she will have a very short maternity leave.

"My maternity leave will be a few weeks long and I'll work throughout it," she said enthusiastically.